1. Field of the Invention
This invention relates to a material removing machine and more particularly to a high speed high pressure belt grinder.
2. Description of the Prior Art
Numerous metal removal apparatus and methods are disclosed in the prior art. Milling machines, vertical spindle grinders, double disc grinders, face broches, and planars have been utilized for removing material from flat planar surfaces. The prior art also includes numerous belt grinding machines for material removal.
U.S. Pat. No. 3,668,814 issued to C. T. Freerks recognizes that with high pressure belt grinder, above a predetermined minimum pressure, metal is removed so swiftly that a large percentage of the heat generated is removed by the chips. This results in a temperature rise of a work piece which is greatly reduced as compared with the temperature rise of the work piece when it is ground at pressures below the predetermined minimum pressure, so that damage to the part and to the abrasive belt is minimized.
It has been recognized that it is desirable to move the grinding belt relative to the work piece for uniform belt wear. This has typically been achieved in the prior art by moving the belt back and forth along the contact and idler pulley. The idler pulley can be shifted to cause this back and forth movement of the grinding belt relative to the contact pulley and idler pulley. I recognized that this type of belt shifting causes premature belt failure since first all the tension is applied to one edge of the belt then the tension is transferred to the other belt edge. This continues as long as the belt is moved back and forth. In my belt grinder I maintain a relatively even tension over the whole belt as compared with other belt tracking systems.
In some prior art grinding machines the work piece is moved upward against the grinding belt by vertical upward movement of the table. This limits the thickness of the work piece. For machines such as this the table is moved by hydraulic cylinders which may introduce inaccuracies as their stroke increases. In my machine the head is moved downward against a vertically fixed table and work piece size is only limited by head clearance.
In other prior art belt grinding machines a cantilevered head is used and this also severely limits workpiece thickness.
The following U.S. Patents are exemplary of prior art belt grinders: (1) U.S. Pat. No. 2,813,382; (2) U.S. Pat. No. 3,132,451; (3) U.S. Pat. No. 3,229,424; (4) U.S. Pat. No. 3,325,947; (5) U.S. Pat. No. 3,394,501; (6) U.S. Pat. No. 3,510,988; (7) U.S. Pat. No, 3,524,285; (8) U.S. Pat. No. 3,739,535; and (9) U.S. Pat. No. 3,908,316.